1. Field of the Invention
The present invention relates to a method of controlling properly an operation of a test hand in an IC handler, which presses an IC device (will be referred to as xe2x80x9cICxe2x80x9d hereinafter) on a contactor of a socket according to the sorts of ICs and contactors, and a measuring and recording system.
2. Description of the Related Art
An IC handler has been in common use as a semiconductor tester. In the IC handler, an IC transferred from the IC loader is placed on the socket of the measuring section. In this state, the pusher of the test hand presses the IC against the socket to bring the contact section of the IC, such as the lead pins, into contact with the contactor of the socket. From the result of electric conduction, the tester judges whether the IC characteristic is acceptable. Then, an unloader separates the IC from the IC handler and holds it.
In recent years, the types of ICs to be tested have been diversified and consequently the types of sockets to hold them have also been diversified. Thus, the operating performance of the test hand should be changed so as to deal with the type of IC and socket. Since the semiconductor tester is requested to process many ICs in a short time, it is desirable that the IC handler should be functioned at high speed. However, the faster the processing speed becomes, the greater the impact of the pusher on the IC when the pusher is pressed against the IC held on the socket, and thus the service life of the lead pins of the IC and the socket contactor may become shorter.
To overcome those problems, a handler, which has been disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-89983, is developed. In this handler, the data of allowable contact pressure in each type of IC has been inputted in a FD (floppy disk) beforehand. When the operator specifies the type of IC, the CPU sends a signal to the control valve on the basis of the data from the FD, thereby the hydraulic cylinder pressure for driving the test hand can be adjusted.
Furthermore, Jpn. Pat. Appln. KOKAI Publication No. 10-227834 has disclosed a mechanism for making fine adjustments to the proper pressure, speed, and displacement of IC pressed into a socket according to the type of IC.
In the above methods currently in use, however, it is required to input IC handler data for each type of IC into the computer in advance. And what is more, these data may be obtained through experience based on the pin pressure per lead pin, the number of pins and the allowable displacement of the socket contactor.
However, since the IC is pressed down by the test hand as it is in a socket, it may not be assured that the values based on the specified data items are always proper. For example, as the working speed of the test hand is increased to process the IC at high speed, the impact on the IC happens and becomes larger when the test hand hits the IC package. In addition, the impact force is likely to exceed the material strength of the IC leads or socket contactor and do damage to the IC package.
As described above, with respect to an IC operation test, the conductivity of an IC has been commonly tested through a contactor provided on a test socket. As a conventional contactor, a probe type contactor using metal pins and a non-probe type contactor using conductive rubber etc. are adopted.
The probe type contactor is composed of two plungers provided on both sides of an extra fine metal tube and a compressive coil spring provided in the tube. In a test by the use of the probe type contactor, metal contact pins sustained by metal springs are employed for probes. Thus, when each probe comes into contact with a projecting solder ball on a contact surface of the IC, some problems arise.
One of the problems is a case where the impact between the solder ball and the tip of the metal contact pin in the probe does damage to the structure and/or function of the IC.
Another problem is a case where a flaw or deformation, which is produced on the surface of the solder ball when the pointed tip of contact pin hits the soft solder ball, results in the malfunction of the IC.
Still another problem is a case where a deformation and/or abrasion of the contact pin due to the numerous iterative tests taken for a long period gives ill effect to the electrical connection with the IC.
When these problems occur, the correct results cannot be expected. In addition, the problems may cause breakage of the IC, or make the service life of the contactor itself shorter.
To eliminate such defects described above, for example, a non-metal type contact probe using conductive rubber, i.e., non-probe type contactor is being developed and comes onto the market in place of the contact probe using the metal pin.
In this sort of contactor, a silicon rubber, which builds in the granular conductive material arrayed columnar, is employed for the contact probe. Since the contact probe made of the conductive rubber is thinner than a conventional socket with metal probe, damage to the surface of the solder balls on the IC can be prevented, and the breakage and abrasion of the IC can be also prevented at the contact with the contactor. In addition, there is an advantage in that the deformation and abrasion of the solder balls can be diminished.
However, there are some weak points in the non-probe type contactor as follows. Since the contactor body is thin, 0.4 mm, for example, its deflection is smaller than that of the coil spring. As the deflection increases, the reaction force of silicon rubber increases in a non-linear manner. When the deflection becomes larger, the array of granular conductive material in the contactor may be broken due to the excessive deformation of rubber.
In general, even if an elastic body is compressed and deformed by the applied pressure, the body is restored to the original size when the external pressure is eliminated. However, it is known that when this deformation and restoring are repeated for many times, the restorability of the elastic body deteriorates gradually and thus the residual deformation increases. In particular, the conductive rubber has a physical feature that its restorability after compression deteriorates earlier than the metal coil spring.
As a rule, when the restorability of the non-metal type or conductive rubber type contact probe is evaluated to be deteriorated, it is required to exchange the contact probe assemblies so as to work without any trouble in a test. However, the non-metal type probe is very expensive. Therefore, a frequent exchange of the contact probe assemblies will cause the increase in production cost of the IC.
In static loading tests for the non-probe type contactor, its P-xcex3-R (reaction force-strain-electrical resistance) characteristics can be specified in advance. However, as described before, there is a problem in that the restorability of rubber deteriorates due to the iteration of compressive loadings by the test hand and thus the deformation remains. That is, the initial P-xcex3-R characteristics of the non-probe type contactor changes with the increase of the number of contacting iteration with the IC in tests.
When the residual deformation exceeds the allotted value, a test cannot be executed normally. Therefore, it should be required to change an expensive assembly of non-probe type contactor when the number of contacting iterations reaches an appointed number of times.
Accordingly, the object of the present invention is to provide an operation method and system for an IC handler to control properly the pushing pressure, operating speed and displacement of the test hand according to the types of IC and socket.
A further object of the invention is to provide a control method and system for an IC handler, through which the non-probe type contactor, e.g., a contactor made of conductive rubber, which can be used for a longer period in comparison with a conventional test, and to execute IC tests properly and at a low cost.
To achieve the foregoing object, the operating method of the working of test hand to control appropriately the pushing force, operating velocity and displacement thereof in the IC handler is invented.
In order to realize the above-mentioned object, the control method of the test hand for pushing the contact of the IC on the socket of the IC handler comprises the step of measuring data by means of sensors through the trial to press an IC on the socket repeatedly by the test hand, so as to obtain data representing the load, the acceleration or velocity, and the amount of thrusting displacement of the test hand until the stoppage thereof after the tip of the test hand contacts with the IC; obtaining the combined spring constant K of the IC socket; and determining the motion of the test hand so as to work the impact force to an IC becoming smaller than the allowable press force.
Furthermore, a control system of the present invention comprises a load sensor for detecting the press force of the test hand applied to an IC; an acceleration sensor for detecting the operating velocity or acceleration of the test hand; a displacement sensor for measuring the thrusting displacement during the time from when the test hand comes into contact with the IC until it stops; and control means for not only calculating the combined spring constant for the IC and a socket on the basis of the data items from the individual sensors, but also controlling the driving of the test hand on the basis of the individual data items so that the press force, velocity, and displacement may reach such values that make the impact force acting on the IC equal to or smaller than an allowed value and speed up the operation of the test hand to the maximum.
A method of controlling an IC handler according to another aspect of the invention, the IC handler which executes a test by pressing down an IC loaded on a test hand against a contactor formed of conductive elastic materials that denotes conductivity in a state of being compressed, comprising:
storing an initial deformation of the contactor;
measuring the residual deformation of the contactor in each test operation; and
giving a warning to replace the contactor when the difference between the amount of initial deformation and that of residual deformation becomes nearly equal to the predetermined allowable amount of deformation.
For example, an IC to be tested is put on a socket and is pressed through the test hand, and the reaction force P against compression and an amount of thrusting displacement D are detected by using sensors provided on the test hand, and then the pressure force and a stroke of the test hand can be determined so that the detected data become equal to or lower than the predetermined allowable values Pa and xcex4a. Furthermore, the position data HC where the IC starts to be pressed is detected, and the difference Z between the HC and an initial value H0 (=H0xe2x88x92HC) is examined whether it is equal to or lower than an allowable amount of residual deformation Za.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.